I had a Fade tourney bag with the quad straps like you do, and I switched over to a Hyzerbomb Flak. I posted a review of it in another thread. Let me tell you though your back is going to do flips when you finally get that backpack on. It sits a lot higher on your back and distributes the weight better. Depending on your disc needs, you could also be stumbling upon a lot of extra room as well. I used to fill up that tourney bag, but in the summer it was real hot, so I would only carry about 8 - 12 discs and have a gallon water cooler in the middle section.

Since I got the flak though I have become sort of a minimalist and now only carry about 6 - 8 discs. Might seem like a waste, but there is now a lot of other stuff I can hold. Most notably the main disc compartment can also house a small cooler, which I can fill with food or drinks or whatever I want/need for the day. Or I could keep that part empty for a winter round and store my extra layers in there. You can probably find other uses for it, but these are the most relevant to me. There are also a lot of other pockets and places to store anything else you really need. The fabric is also pretty good too I have had mine since August and it's holding together pretty well so far. I highly recommend one.

I have been carrying a Grip bag for the last 2 years. It is hands down the best bag I ever owned. The strap configuration is much more comfortable than any added after market strap. The cushioning on the shoulders and lower back is great, and pocket sizes for gear are roomy. You can easily carry snacks, rain gear, with plenty of room for extra towels, and easily holds 2 Nalgene sized water bottles. Plus your back will be saved, it's light weight but durable. You will not be disappointed, and the original is on sale for $222 right now...limited colors. Hope this helps.